Automatic drain valve



p 26, 1939- B. s. AIKMAN ,926

AUTOMATIC DRAIN VALVE FiledJune 10, 1937 6 0O 6 o: 30 3 2% 1r '42 /0 9 n j} r lll "In INVENTOR BURTON E. AIKMAN ATTORNEY '10 during operation of the brake equipment.

Patented Sept. 26, 1939 UNITED STATES PATENT OFFICE 2,173,926 AUTOMATIG DRAIN VALVE Application June 10, 1937, Serial No. 147,413

7 Claims.

This invention relates to an automatic drain valve adapted to be employed with the reservoir or receiver of a fluid pressure system to drain moisture which accumulates in the reservoir.

In the operation of fluid pressure systems, such as a fluid pressure brake system, air from the atmosphere is compressed and is stored in a reservoir or receiver from which fluid is withdrawn As a result of the supply of fluid under pressure to and the release of fluid under pressure from the reservoir, water is deposited in the reservoir, and unless it is periodically drained away it 1'5 accumulates in the reservoir and reduces the volume of the reservoir, while it may freeze and cause injury to the equipment.

It is an object of this invention to provide a drain valve adapted to be employed with the reservoir of a fluid pressure system to automatically release liquid which accumulates in the reservoir.

A further object of the invention is to provide a drain valve of the type described and incorporating a chamber adapted to hold moisture which collects in the reservoir, together with a passage through which fluid is supplied from .a compressor to reservoir, and arranged so that the fluid flowing through the reservoir will heat the moisture collected in the chamber to thereby prevent freezing of the moisture and maintain .it in a liquid form.

Another object of the invention is to provide 'an improved drain valve of the type described which may be easily attached to a reservoir of the type employed in fluid pressure systems.

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accom- Mo panying drawing, in which Fig. l is a sectional view of a reservoir equipped with the improved drain valve provided by this invention, and

.Fig. 2 is a top view of the piston employed in ,45 the drain valve shown in Fig. 1.

555 wall of the reservoir I surrounding the opening tion until a predetermined pressure differential 2, while a gasket 6 is interposed between the flange 5 and the reservoir.

The body of the drain valve 4 has a passage indicated at 8 formed therein, while one end of this passage is surrounded by threads, indicated 5 at 9, and adapted to receive the threaded end of a pipe I0 leading from a compressor, not shown. The otherend of the passage 8 is adapted to receive a tube I2, which, when the drain valve is secured to the reservoir I, extends up- 10 wardly into the reservoir.

The body of the drain valve 4 has an annular recess I4 therein outwardly of the tube I2, and the bottom of this recess is vertically beneath the top wall of the tube I2. A strainer in the form of a perforated metal cylinder indicated at I5 is mounted in the recess i4, and extends within the reservoir I. The strainer I5 permits water to flow fromthe lower portion of the reservoir I to the recess I4, but prevents large v'2; particles of foreign matter from reaching the recess l4.

Thebody of the drain valve 4 has an annular chamber, indicated at I6, formed therein, while a face of the wall of the passage 8 is exposed to the space within the chamber I6.

The inner face of the inner wall of the chamber I6 has threads formed therein as indicated at I8, and adapted to receive complementary threads formed upon a cap member 20. The member 28 has a flange 2| thereon, while a sealing gasket '-22 is interposed between the flange ;2I and the lower face of the lower wall of the chamber I6 to prevent leakage of fluid through the joint atthis point.

The cap member 20 has a substantially tubular portion 23 having a bore therein in which is mounted a loosely fitting piston 24 having formed integral therewith a stem 25, which carries at the upper end thereof a fluted guide portion 26. The flutes or grooves in the guide portion 26 permit free flow of fluid between the area at the face of the piston 24, and the chamber 28 between the cap member 20 and the lower wall of the passage 8, and which is open by way v of a passage 30 to the lower portion of the recess Hi, and thereby to the reservoir I.

The piston 24 has a groove therein in which is mounted a piston ring 32 which is yieldingly held in engagement with the face of the bore in which the piston is mounted. The piston ring 32 frictionally resists movement of the piston 24, and prevents its movement in either direcis developed in the chambers at the opposite faces of the piston 24.

The piston 24 has formed integral therewith a valve 33 having a seating face adapted to seat upon a seat surrounding a passage 35 leading to the atmosphere from the chamber 34 at the lower face of the piston 24.

The tubular portion 23 of the cap member 20 has ports or passages indicated at 36 extending therethrough, while the inner wall of the chamber I6 has ports or passages 31 formed therein adjacent the lowermost portion of the chamber I5 so that the chamber 34 is constantly connected with the chamber I6.

The drain valve 4 has a valve chamber 38 formed therein in which is mounted a ball check valve 39, which is adapted to seat upon a seat surrounding a passage 40 open to the chamber 28, at a point vertically beneath the upper wall of the chamber I6,

The valve chamber 38 is open to the upper portion of the chamber I6 by way of a passage 42, while the ball check valve 39 is yieldingly pressedto the seated position by means of a spring 44 which extends between the ball check valve 39 and a threaded cap 45. The spring 44 is proportioned so as to maintain the ball check valve 39 in the seated position to prevent flow of fluid through the passage 40 to the valve chamber 38, and thence by way of the passage 42 to the chamber I6, until the pressure of the fluid in the chamber 28 has been increased above the pressure of the fluid in the chamber I6 by an amount somewhat greater than the amount which is required to overcome the frictional resistance of the piston ring 32 and move the piston 24 to cause the valve 33 to be moved to the seated position.

In initially charging the system, fluid under pressure is supplied from a compressor, not shown, by way of the pipe I8, and flows through the passage 8, and through the passage within the tube I2 to the reservoir I, and charges this reservoir with fluid under pressure. The fluid supplied by way of the passage ID to the passage 8 is heated as a result of having been compressed, and this heat is imparted to the walls of the passage 8 to increase the temperature of these walls, while the heat supplied to these walls is transmited to the chambers I6 and 28 with the result that any moisture present in the chambers I6 and 28 will be maintained in a liquid form.

On the supply of fluid under pressure to the reservoir I, fluid flows therefrom by way of the passage 30 to the chamber 28, and through the grooves in the guide portion 26 to the area at the upper face of the piston 24, and causes this piston to be moved downwardly and press the face of the valve 33 to the seated position to cut ofl communication between the chamber I6 and the atmosphere.

On an increase in the pressure of the fluid in the chamber 28 to a predetermined. value above the pressure of the fluid in the chamber I6, the ball check valve 39 is moved against the spring '44, and fluid flows to the valve chamber 38, and

thence through the passage 42 to the chamber I6 until the pressure of the fluid in the chamber I6 has been increased to the predetermined value below the pressure present in the chamber 28 and in the reservoir I. The spring 44 thereupon moves the ball check valve 39 to the seated position to cut ofi the further flow of fluid through the passage 40 to the chamber I6, and thereafter fluid under pressure leaks at a slow rate past the piston 24 to the chamber 34, and to the chamber I6, until the pressure of the fluid in the chambers 34 and I6 is increased substantially to the pressure of the fluid in the reservoir I. At this time, the pressure of the fluid in the chambers at the opposite faces of the piston 24 being substantially equal, the valve 33 is held in the seated position by the fluid under pressure in the chamber 28 operating upon an area of the piston 24 substantially equal to the area within the seating face of the valve 33.

Any liquid which is deposited in the reservoir I during operation of the system will flow by gravity to the lower portion of the reservoir, and through the passages in the perforated cylinder I5 to the recess I4 outwardly of the tube I2, and thence by way of the passage 30 to the chamber 28.

The tube I2 extends within the reservoir I far enough so that during normal operation, the water will not accumulate in the reservoir I to a level to overflow the top edge of the tube I2, nor

to reach this tube as a result of splashing or movement of the water caused by the movement of the vehicle on which the equipment is mount- On a subsequent reduction in the pressure of the fluid in the reservoir I, such as may be occasioned by the withdrawal of fluid under pressure from this reservoir, there is a corresponding reduction in the pressure of the fluid in the chamber 28, which is constantly open to the reservoir I through the passage 30, while the ball check valve 39 prevents back flow of fluid from the chamber I6, with the result that the 1' pressure of the fluid in the chamber I6 is maintained at the pressure to which this chamber has been charged.

Accordingly on this reduction in the pressure of the fluid in the reservoir I and in the chamber- 28, the higher pressure of the fluid in the chamber 34, which is open to the chamber I6, moves the piston 24 upwardly against the resistance of the ring 32 until the guide portion 26 engages a projection 41 formed on the body portion of thedrain valve, while the valve 33 is moved away from the seat surrounding the passage 35, and fluid is released from the chamber I6 through the passage 35 to reduce the pressure of the fluid in the chamber I6.

The piston ring 32 operates to prevent downward movement of the piston 24 until the pressure of the fluid in the chamber I6 has been reduced to a value somewhat below the pressure of the fluid in the chamber 28, and when the pressure of the fluid in the chamber I6 has been reduced to this value by the release of fluid through the passage 34, the resistance of the ring 32 is overcome and the piston 24 is moved downwardly and moves the valve 33 to the seated position to cut olf the further release of fluid under pressure from the chamber I6. At this time, while the pressure of the fluid in the chamber 28 is somewhat greater than the pressure of the fluid in the chamber I6, the pressure ofnot move to the open position until the pressure differential between the chambers 28 and I6 is somewhat greater than is required to move the piston 24 against the resistance of the piston ring 32.

If, after the valve 33 has been moved to the seated position, there is a further reduction in the pressure of the fluid in the reservoir l, and therefore in the chamber 28, the piston 24 will again be moved upwardly into engagement with the projection 41, while the valve 33 will be moved away from its seat to again permit the release of fluid under pressure from the chamber IS with the result that the pressure of the fluid in the chamber I6 is again reduced to a predetermined value below the pressure of the fluid in the chamber 28, whereupon the piston 2 is again moved downwardly to move the valve 33 to the seated position.

At this time the pressure of the fluid in the chamber 28 exceeds the pressure of fluid in the chamber I6, and any liquid which may have accumulated in the lower portion of the reservoir l flows therefrom by way of the passage 30 to the chamber 23, and to the area of the upper face of the piston 24. This liquid will leak past the piston 24 to the chamber 34, and therefrom to the chamber l6 until the pressure of the fluid in the chamber l6 has been increased to the pressure of the fluid in the chamber 28 and in the reservoir 1. The liquid which leaks past the piston 24 flows through the passages to the lower portion of the chamber l5, and rises upwardly in the chamber l6, while the gaseous fluid trapped in the upper portion of the chamber it is compressed until the pressure of this gas is increased to the pressure of the fluid in the chamber 28, and in the reservoir l.

The water which flows from the reservoir l to the chamber 28 will flll the chamber 28 to a level above the lower end of the passage to thereby seal this passage. If at this time the ball check valve 39 does not seat perfectly so that fluid under pressure in the upper part of the chamber it may leak past the valve 39 to the passage 40, the gas cannot flow through the passage 40 to the chamber 28, and through the passage 30 to the reservoir l. Gaseous fluid will always be trapped in the upper portion of the chamber 56, and liquid cannot rise in the chamber 16 above a predetermined level, even though the ball check valve 39 does not seat perfectly.

On a subsequent increase in the pressureof the fluid in the reservoir I, which may be occasioned by the supply of fluid under pressure thereto from a compressor, not shown, through the pipe H] and the passage 8, the higher pressure of the fluid in the reservoir l operating upon the liquid accumulated in the lower portion of the reservoir, and in the passage 3!], will cause the ball check valve 39 to be moved against the spring 44 to permit the supply of fluid, either gaseous or liquid, depending upon the amount of liquid in the reservoir, through the passage 40 to the chamber 38, and through the passage 42 to the chamber l6, until the pressure of the fluid in the chamber l6 has been increased to within a predetermined value of the pressure in the reservoir I. When the pressure of the fluid in the chamber I6 has been increased to this value, the ball check valve 39 is moved to the seated position, while the pressure of the fluid in the chamber I6 is thereafter increased substantially to the pressure of the fluid in the reservoir I by leakage past the piston 24, as explained above.

On a subsequent reduction in the pressure ent, is:

of the fluid in the reservoir I, there is a reduction in the pressure exerted upon the liquid or gas present in the chamber 28, and if the pressure of the fluid in the chamber 28 is reduced to a predetermined value below the opposing On the release of liquid from the chamber I6,

the gas present in the upper portion of this chamber expands, thus reducing the pressure exerted thereby and correspondingly reducing the force exerted on the piston 24.

v When the pressure of the fluid in the chamber 34 at the lower face of the piston 24 is reduced to a predetermined value beneath the opposing pressure in the chamber 28, the piston 24 is (2'0 moved downwardly, while the valve 33 is moved to the seated position to cut oh" the further release of liquid or gas from the chamber [6.

Thereafter the pressure of the fluid in the chamber 16 is increased byleakage past the piston .24, or by flow past the check valve 39, as explained in detail above.

It will be seen that the body of the drain valve has a passage therein through which fluid is supplied from the compressor to the reservoir, with the result that the heat of compression imparted to the fluid by the compressor will be transmitted to the body of the drain valve, and will heat it sufliciently so that moisture present in the chamber in the body, or in the passages associated therewith, and in the lower portion of the reservoir l, will be maintained in a liquid form in freezing weather. As a result, therefore, the drain valve will not be rendered inoperative because of freezing of the liquid present therein, or in the reservoir.

It will be seen that the drain valve provided by this invention operates automatically in response to Variations in the pressure of the fluid in the reservoir to drain liquid from the reservoir,

and the various parts of the drain valve may be arranged and proportioned so that the quantity of liquid released from the reservoir on each operation of the drain valve will be large enough to maintain the reservoir substantially free of liquid at all times, while at the same time the quantity of fluid discharged through the drain valve on each operation thereof will not be so great as to unduly deplete the supply of fluid present in the reservoir.

While one embodiment of the improved drain valve provided by this invention has been illustrated and described in detail, it should be understood that the invention is not limited to these details of construction, and that numerous changesand modifications may be made without departing from the scope of the following claims.

Having now described my invention, what I claim as new and desire to secure by Letters Pat- 1. In a device of the class described, in combination, a body adapted to be secured over an opening in the lowermost portion of a reservoir or the like, said body having a passage therein having one end open to the reservoir, the other end of said passage being adapted to have connected thereto a pipe leading from a compressor, the end of the passage open to the reservoir being surrounded by a substantially vertical wall, the body having outwardly of said wall and surrounding said wall a'recess the bottom of which is at a lower level than the top edge of said wall, said body having a chamber therein, a communication through which liquid may drain from said recess to said chamber,'and valve means responsive to variations in the pressure of the fluid in said reservoir and controlling a passage through which liquid may drain from said chamber.

2. In a device of the class described, in combination, a body adapted to be secured over an opening in the lowermost portion of a reservoir or the like, said body having a supply passage therein having one end open to the reservoir, the other end of said passage being adapted to have connected thereto a pipe leading from a compressor, the end of the passage open to the reservoir being surrounded by a substantially vertical wall, the body having outwardly of said wall and surrounding said wall a recess the bottom of which is at a lower level than the top edge of said wall, said body having a chamber therein, a communication through which liquid may drain from said recess to said chamber, a wall of said supply passage being exposed on one side to said chamber, whereby the heat of compression of the fluid flowing through said passage from the compressor to the reservoir is readily imparted to liquid in said chamber to maintain it in liquid form, and valve means controlling a passage through which liquid may drain from said chamber.

3. In an automatic drain valve for use in a fluid pressure system, a body having a bore therein and having a chamber formed therein and adapted to contain fluid under pressure, a piston mounted in said bore, the area at one face of said piston being open to said system and the area at the other face of the-piston being connected to said chamber only at a point adjacent the lowermost portion of said chamber, valve means operated by said piston and controlling a passage through which liquid may drain from said chamber, a passage through which liquid may drain from said system to said chamber, and a check valve operative to prevent back flow of fluid from the chamber to the system through said passage.

4. In an automatic drain valve for use in a fluid pressure system, a body having a bore therein and having a chamber formed therein, a piston mounted in said bore, the area at one face of said piston being subject to the pressure of the fluid in said system and the area at the other face of the piston being connected to said chamber only at a point adjacent the lowermost portion of said chamber, valve means operated by said piston and controlling a passage through which liquid may drain from said chamber, a passage through which liquid may drain from the system to said chamber. andya check valve operative to prevent back flow of fluid from the chamber to the system through said passage, said check valve being also operative to prevent flow of fluid from the system to said chamber until a predetermined pressure differential is established between the system and said chamber.

5. In an automatic drain valve for use in a fluid pressure system, in combination, a body having a bore therein, a piston mounted in said bore, said piston being subject on one face to the pressure of the fluid in the system and being subject on the other face to the pressure of the fluid in a chamber, a valve operative by said piston and controlling a passage through which liquid may drain from said chamber, means associated with said piston and friotionally opposing movement of said piston, said means being operative to prevent movement of said piston until a predetermined pressure differential is established between thepressures in the system and in said chamber, and valve means operative only on an increase in the pressure of the fluid in the system to produce a higher differential than said predetermined diiferential between said system and said chamber to open a communication through which liquid may drain from the system to said chamber, said valve means being operative to prevent back flow of fluid from said chamber to said system.

6. In an automatic drain valve for use in a fluid pressure system, in combination, a body having a bore therein, a piston mounted in said bore, said piston being subject on one face to the pressure of the fluid in the system and being subject on the other face to the pressure of the fluid in a chamber, a valve operative by said piston and controlling a passage through which .liquid may drain from said chamber, means associated with said piston and frictionally opposing movement of said piston, said means being operative to prevent movement of said piston until a predetermined pressure differential is established between the pressures in the system and in said chamber, and valve means operative only on an increase in the pressure of the fluid in the system to produce a higher differential than said predetermined differential between said system and said chamber to open a communication through which liquid may drain from the system to said chamber, said valve means being operative to prevent back flow of fluid from said chamber to said system, said piston being appreciably smaller in diameter than said bore, whereby fluid from the system may leak past the piston to said chamber at a restricted rate.

7. In an automatic drain valve for use with a fluid pressure system, in combination, a body having a chamber therein adapted to contain fluid under pressure, said body having a bore therein, a piston mounted in said bore, the area at one face of said piston being supplied with fluid under pressure from said system and the area at the other face of said piston being open to said chamber by way of a passage which communicates with said chamber only adjacent the lowermost portion thereof, a valve operated by said piston and controlling a passage through which fluid may be released from said chamber, a communication through which liquid may drain from said system to said chamber, the upper wall of said communication at one point therein being disposed vertically beneath the upper wall of said chamber, and a check valve operative to prevent back flow of fluid through said communication.

' BURTON S; AIKMAN. 

